This invention relates to asphalt-based roofing materials, and in particular to a roofing material having improved durability and impact resistance to withstand the destructive forces of storms.
Asphalt-based roofing materials, such as roofing shingles, roll roofing and commercial roofing, are installed on the roofs of buildings to provide protection from the elements. Typically, the roofing material is constructed of a substrate such as a glass fiber mat or an organic felt, an asphalt coating on the substrate, and a surface layer of granules embedded in the asphalt coating.
The typical roofing material construction is suitable under most circumstances. However, sometimes a roofing material is subjected to environmental conditions that may damage the roofing material. For example, storms are responsible for billions of dollars in damage to roofing materials every year. During storms, hailstones may impact the roofing material, which may cause tears or punctures in the roofing material. The hailstone impacts may also cause an immediate loss of some granules from the impacted areas of the roofing material and a further loss of granules from those areas over time. The loss of granules creates an unattractive appearance and leaves the asphalt coating in those areas unprotected from the degrading effects of the elements. Accordingly, there is a need for a roofing material having an improved ability to withstand the destructive forces of storms.
The prior art does not adequately address the need for a storm proof roofing material. For example, U.S. Pat. Nos. 5,380,552 and 5,516,573, both issued to George et al., disclose a method of improving the adhesion of granules to a roofing shingle, by spraying a thin stream of a low viscosity adhesive to cover 50-75% of the surface of the asphalt coating before applying the granules. The patents teach that granule loss is caused by moisture disrupting the bond between the granule and the asphalt coating. There is no suggestion that granule loss may be related to changes in the asphalt coating over time, or that sufficiently covering the asphalt coating with the adhesive may reduce these changes and the resultant granule loss.
It is known to apply a surface coating onto a roof after the roofing shingles have been installed to protect the shingles from granule loss and other damage. Unfortunately, surface coatings require additional labor to apply after the roofing shingles have been installed, they are relatively expensive, and they may create safety problems by producing a slick roof.
Several patents disclose roofing materials constructed with multiple substrates. For example, U.S. Pat. No. 5,326,797, issued to Zimmerman et al., discloses a roofing shingle including a top mat of glass fibers and a bottom mat of polyester. The patent is related to a fire-resistant shingle, and there is no mention of improved impact resistance. Also, there is no suggestion of improved bonding between the polyester mat and the asphalt coating.
U.S. Pat. No. 5,571,596, issued to Johnson, discloses a roofing shingle including an upper layer of directional fiber such as Kevlar fabric, a middle layer of fibrous mat material such as glass fiber mat, and a lower layer of directional fiber such as E-glass fabric. The upper fiber layer is described as being important to shield the shingle from hail impact damage. The lower layer of E-glass fabric is not effective for improving the impact resistance of the shingle.
U.S. Pat. No. 5,822,943, issued to Frankoski et al., discloses an asphalt-coated roofing shingle including a scrim and a mat. The scrim is bonded to the mat with adhesive; there is no suggestion of improved bonding between the scrim and the asphalt coating. A scrim is not very effective for improving the impact resistance of a roofing shingle.
A journal article, xe2x80x9cBallistic Impact Resistance of SMA and Spectra Hybrid Graphite Compositesxe2x80x9d, Journal of Reinforced Plastics and Composites, Vol. 17, 2/1998, by Ellis et al., discloses placing energy absorbing fibers on the back surface of a graphite composite. The fibers were found to provide only a slight improvement in the impact strength of the composite. The journal article is not related to roofing materials.
It is known to manufacture roofing materials with rubber-modified asphalt to provide some improvement in impact resistance. Unfortunately, roofing materials made with rubber-modified asphalt are more difficult to manufacture, handle, store and install, and they are more expensive, than roofing materials made with conventional roofing asphalt. Also, the rubber-modified asphalt shingles are not very effective in resisting impacts. Accordingly, there is still a need for a roofing material having improved durability and impact resistance to better withstand the destructive forces of storms.
The above objects as well as others not specifically enumerated are achieved by an asphalt-based roofing material according to the present invention. The roofing material includes a substrate coated with an asphalt coating, a protective coating adhered to the upper surface of the asphalt coating, a surface layer of granules adhered to the protective coating, and a web bonded to the lower region of the asphalt coating. The combination of the protective coating and the web provides a roofing material having both improved durability and improved impact resistance. As a result, the roofing material is better able to withstand the destructive forces associated with storms.
In another embodiment, the roofing material includes a substrate coated with an asphalt coating, a protective coating adhered to the upper surface of the asphalt coating, and a surface layer of granules adhered to the protective coating. The protective coating covers at least about 80% of the upper surface of the asphalt coating in the exposed portion of the roofing material.
The present invention also relates to a method of manufacturing the storm proof roofing material. The method includes the steps of coating a substrate with an asphalt coating, applying a protective coating to the upper surface of the asphalt coating, applying a surface layer of granules to the protective coating, and applying a web to the lower region of the asphalt coating.
In another embodiment, the method includes the steps of applying a web to a substrate, coating the substrate and the web with an asphalt coating, where the web is in contact with the lower region of the asphalt coating, applying a protective coating to the upper surface of the asphalt coating, and applying a surface layer of granules to the protective coating.
In another embodiment, the method includes the steps of coating a substrate with an asphalt coating, moving the asphalt-coated substrate at a speed of at least about 200 feet/minute (61 meters/minute) past an applicator to apply a continuous layer of protective coating to the upper surface of the asphalt coating, and applying a surface layer of granules to the protective coating. The rapid movement of the asphalt-coated substrate creates a boundary layer of air on the upper surface of the asphalt coating, which can create discontinuities in the protective coating. The applicator is positioned sufficiently close to the upper surface of the asphalt coating to minimize the boundary layer and thereby substantially reduce discontinuities in the protective coating.
In a further embodiment, the method includes the steps of coating a substrate with an asphalt coating, providing a solid or molten film of a protective coating material, applying the film to the upper surface of the asphalt coating, and applying a surface layer of granules to the film.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.